The present invention relates to a method of correcting an amplitude defect of an Mo/Si multilayer film or an Mo2C/Si multilayer film of an EUVL mask by a focused ion beam.
At present, an optical projection exposure apparatus using KrF of wavelength 248 nm or an ArF eximer laser of wavelength 193 nm is used in a pattern transcription to a wafer. Recently, there is reported a possibility of capable of dealing with till 65 nm rule or 45 nm rule in half pitch by using in combination a liquid immersion technique in which a resolving power is improved by filling between an objective lens of the projection exposure apparatus and the wafer with a medium of high refractive index and an ultra-resolution technique such as deformation illumination and Levenson-type phase-shift mask. However, on and after 32 nm rule, since it reaches a resolution limit, there is proposed a new transcription method like a soft X-ray reduction exposure (Extreme Ultra Violet Lithography, EUVL) in which an exposure wavelength has been extremely shortened. The EUVL is a technique for performing the exposure by reducing the soft X-ray of about 13.5 nm in wavelength to ¼ by a reflection optical system and deemed to be a limit of shortening the wavelength of an ultraviolet exposure, and recently it especially gets attention as a lithography technique capable of being utilized over two or more generations of 45 nm rule or on and after 32 nm rule.
An EUVL mask is constituted by an Mo/Si multilayer film consisting of by-layers of 40–60 layers of about 7 nm cycles in which Mo and Si have been alternately laminated in order to reflect an EUV light having entered onto a low expansion glass (quartz) substrate, an absorber of about 70 nm made of a binary or ternary film containing a heavy metal, such as TaN or TaBN or TaGeN, bearing a function of absorbing the EUV light and transcribing a pattern shape, and a buffer layer which exists between the absorber and the Mo/Si multilayer film and is made of SiO2 or Cr or CrN of about 30 nm for protecting the Mo/Si multilayer film at a dry etching time of an absorber pattern (Non-patent Document 1). Since the Mo/Si multilayer film is weak against a heat and there is required a manufacturing process whose temperature is considerably low and there is also a variation with time, recently there is proposed also the Mo2C/Si multilayer film which is excellent in its heat resistance and in which no variation with time exists (Non-patent Document 2).
As to the EUVL mask, besides a pattern abnormal defect of the absorber pattern, there is reported a defect of the Mo/Si multilayer film (or Mo2C/Si multilayer film). It is known that, in the defect of the Mo/Si multilayer film (or Mo2C/Si multilayer film), there are the amplitude defect (this decreases an intensity of EUV reflected light) generated by the fact that a foreign matter and the like are mixed in a place near a multilayer film surface, and a phase defect generated by the fact that the foreign matter and the like are mixed on a glass substrate or at an initial time of a deposition of the multilayer film (Non-patent Document 3). It is necessary that the amplitude defect and the phase defect are removed before film-forming the absorber and the buffer layer. There is also proposed a method of detecting the amplitude defect and the phase defect while distinguishing them by utilizing a difference in through-focus characteristic of the light (Non-patent Document 3).
As to the defect of the absorber pattern of the EUVL mask, there is reported a method of correcting it by the focused ion beam similarly to a photomask. As a method of correcting the amplitude defect of the Mo/Si multilayer film (or Mo2C/Si multilayer film), there is proposed a correcting method by an etching of the foreign matter in the multilayer film by a low acceleration Ar beam and a capping layer formation for Mo film oxidation prevention by an Ar beam Si sputter film (Non-patent Document 3). As a method of correcting the phase defect of the Mo/Si multilayer film (or Mo2C/Si multilayer film), there is proposed a method of correcting it by forming silicide in an Mo/Si interface by heating by an electron beam to thereby relieve a step having been generated in the Mo/Si multilayer film (Non-patent Document 3).
In the above proposed method of correcting the amplitude defect of the Mo/Si multilayer film (or Mo2C/Si multilayer film), although the Ar ion beam of 500 V is used, since a gas ion source is large in its light source size and additionally used in the low acceleration, it is impossible to converge the ion beam, so that there has been a problem that a foreign matter periphery is widely shaved. Further, there have been problems that, in order to film-form the capping layer, it is necessary to dispose an Si target for the sputter to a suitable position near the mask, additionally it is also necessary to adjust sputtered Si so as to be deposited to a desired position, and further an Si film is adhered to an unnecessarily wide region because it is a sputter film.
[Non-patent Document 1] T. Shoki, T. Kinoshita, N. Sakaya, M. Hosoya, R. Ohkubo, Y. Usui, H. Kobayashi, and O. Nagarekawa, J. Vac. Sci. Technol. B21 3021–3026 (2003)
[Non-patent Document 2] S. Yulin, T. Kuhlmann, T. Feigal, and N. Kaiser, Proceedings of SPIE 4343 607–613 (2001)
[Non-patent Document 3] A. Barty, P. B. Mirkarimi, D. G. Stearns, D. Sweeney, H. N. Chapman, M. Clift, S. Hector, and M. Yi, Proceedings of SPIE 4688 385–394 (2002)
It is an object of the present invention to correct the amplitude defect in the Mo/Si multilayer film or the Mo2C/Si multilayer film of the EUVL mask.